1. Field of the Invention
The present invention relates to a totally-solid lithium secondary battery which uses a lithium ion conductive solid electrolyte as an electrolyte, and a transition metal chalcogenide or a lithium.cndot.transition metal chalcogenide as an active material for negative electrode.
2. Description of Related Art
With recent development of portable equipment such as personal computers, portable telephones, etc., demand for batteries as electric sources thereof much increases. Particularly, lithium batteries are intensively investigated in various fields as batteries capable of providing high energy density because lithium has a small atomic weight and has a large ionization energy.
As active materials for electrodes used in lithium batteries, for example, iron disulfide performs a four-electron reaction as shown in the following formula 1, and shows a high theoretical capacity density of 894 mAh/g. EQU FeS.sub.2.revreaction.Li.sub.3 Fe.sub.2 S.sub.4.revreaction.Li.sub.2+x Fe.sub.1-x S.sub.2 +Fe.sub.1-x S.revreaction.Li.sub.2 FeS.sub.2.revreaction.Li.sub.2 S+F 1
Moreover, when the transition metal element is cobalt or nickel, the four-electron reactions shown in the following formulas 2 and 3 also take place, and a high theoretical capacity density is obtained. EQU CoS.sub.2.revreaction.Co.sub.3 S.sub.4.revreaction.Co.sub.x S.sub.9.revreaction.Co 2 EQU NiS.sub.2.revreaction.NiS.revreaction.Ni.sub.7 S.sub.6.revreaction.Ni.sub.3 S.sub.2.revreaction.Ni 3
However, reversibility of these reactions is low, and is insufficient for practical secondary batteries.